Pulse jet engine



April 1961 R. R. CURTIS 2,979,901

PULSE JET ENGINE 2 Sheets-Sheet 1 Filed Sept. 2, 1958 April 18, 1961 R. R. CURTIS PULSE JET ENGINE 2 Sheets-Sheet 2 Filed Sept. 2, 1958 25 in E fiYJ EH/UF @USSAZZ. Q C l/@775 PULSE JET ENGINE Russell R. Curtis, Indianapolis, Ind., assignor to Curtis Automotive Devices, Inc., Westfield, Ind., a corporation of Ohio Filed Sept. 2, 1958, Ser. No. 758,245

5 Claims. c1. 6039.77)

vide a new and improved pulse jet engine having means associated therewith effective to restrict the combustion volume, accomplish greater compression, and thereby promote more eflicient engine operation.

Another object of this invention is to promote the starting of a pulse jet engine by provision therein of a collection chamber for the starting mixture and by pro viding a ring of turbulence to hold the residual flame for re-ignition.

Another object'of the invention lies in the utilization of shield means interiorly of a pulse jet engine functioning to promote smoother combustion and to thereby re duce the engine noise level and eliminate irritating frequencies thereof.

Still another object of the present invention is to provide baffle means within the combustion chamber of a pulse jet engine which directs the fuel-air mixture against the chamber walls and thereby preheats the mixture prior to ignition thereof.

A further object of this invention lies in the provision of shield means spaced from theyalve means in a pulse jet engine, the bafiie means substantially increasing the life of the valve means by reducing the temperature thereof and absorbing shocks directed thereagainst. I

An even'further object of this invention is to provide an engine of the pulsating jet type supportingbafilemeans within the combustion chamber thereof spaced from the valve means and the combustion chamber-walls, the combustion chamber being thereby divided into two compartments the respective volumes of which are closely related, and the baffle means being surrounded by an annular gap the area of which is closely related to the combustion chamber cross-sectional area.

Other objects-and advantages of this invention will'rbe come more apparent during the course of the following description, particularly when taken in connectionvvith the accompanying drawings. v 1 1 In the drawings, wherein likenhrnerals are employed to designate like parts throughout the same: i

Figure 1 is a side elevational view of apulse jet en- 2,979,901 Patent d A 1 2 other. manner of supporting the baflle means interiorly of the combustion chamber; Figure v6 is a top plan view of the baffle means of Fig ure 5; and 7 Figure 7 is a detail sectional view to more clearly illus trate the baffle supporting means of Figures Sand 6.

Briefly stated, the present invention is directed prin -b cipally to a new and improved pulse jet engine having in' the combustion chamber thereof bafile means effective to essentially entirely eliminate damage to the valve means due to over-heating or over-stressing, and to improve substantially the engine performance. or shield device may take various forms and shapesya preferred configuration features a relatively flat face portion spaced axially from the valve means and radiallyinwardly of the combustion chamber walls. The cross sectional outline of the baffle means conforms to the con figuration of the combustion chamber inner diameter to provide an annular gap which is uniform, the gap area being preferably one-fourth to one-half of the combustion chamber cross-sectional area. By provision of shield means of the character herein disclosed, the combustion chamber is divided into an entry compartment and a flame compartment, the volume of the former being pref erably 10 to 25% of the volume of the latter compart merit. Other structural features of the present invention will become apparent during the course of the description now to follow. v

Referring now to Figures 1 and 2, there is shown a jet unit 10 comprising a combustion chamber 11 connected by a converging section 12 to a jet pipe 13 terminating in an orifice 14. A combined air intake and valve assembly ceived in a flange portion 17 of the valve assembly and threaded into a valve seat plate 18 and a ring member 19 'welded or otherwise secured to the inner walls of the combustion chamber.

The plate 18 has a plurality of intake ports 20-con'- nected by an annular intake passage that converges to form a venturi section 21 having a forwardly flared air intake mouth portion 22. The ports 20 are covered by a valve 23of petal configuration, one valve petal or flapper being over eachof the valve ports 20. The valve 23 is held in place by 'a'curved-backstop 24 receiving bolt means or the like 25 threaded at one end into the center of the valve seat plate 18 and base of a generally conical central part 26. Extending through the venturi section 21 isfuel pipe 27 having one or more fuel orificesl28',

the pipe 27 being preferably threaded as at 29 into the which a hose 31 is attachedfor 'introducin'gair under pressure into the venturi section 17 for starting, A

source of air pressure causes air to pass over the holes 32 from a fuel supply tank "(not shown) and, ejecting it j glue of the general'character with which the present invention is of important application;

Figure 2 is a fragmentarycross-sectional view' er a portion of a pulse jet engine, having incorporated therein a device constructed in accordance with-the principles of this invention;'

Figure 4 is a vertical 'ectional a r ews ti r t9 'Fis 28 in the fuel pipe 27, thereby drawing fuel through hose from theholes 28in a spray.

ports 20 and lifts the petals of -the valve 23' sufficiently to permit the combustible mixture to enter the combustion chamber 11. A spark plug 33 ignites-the mixture, and

' as, combustion starts, the valve- 23 closesagainst ;the

Figure 3 is a vertical sectionalfview taken s'ubstantially "m ,".l. l

"sufficient to draw the fuel Tout -plate "18 due to its own resiliency and the force of the explosion. The explosion sets up a blast through the "jet pipe 13, and the blast, in traveling down said pipe causes -'an'-'inject'or suctionwhich draws fresh air through the venturi section 21'. The flow of air through the venturiis the orifices 28 and' pro vide a combustible mixture. Thefc'ombustible jmixture f ar b s h ou h th .;.1, 5 ew; rmane The blast of air and fuel then-continues through the awe-9.01

- a chamber 11, is ignited therein; and the cycle repeated with extreme rapidity. Ignition is automatic thereafter.

It will now be appreciated that the valve petals 23 during the cycle described are subjected to substantial temperatures and stresses, resulting in a relatively short life for the valve means. Further, pulse jet engines in general are characterized by a relatively high noise level during operation, which is an annoyance to the operator and persons in the vicinity of the jet engine. Applicant has discovered, however, that valve life may be markedly increased and the performance of the engine substantially improved by provision of shield or baffle means located in the combustion chamber radially spaced inwardly from the walls thereof downstream from the petal valve.

The baffle or shield means may take various forms and shapes, and one exemplary embodiment thereof is designated generally in Figures 2 and 3 by the numeral 34. The baffle means is preferably constructed of stainless steel, and may be in the form of a generally circular flat disc or may have an essentially hemispherical configuration as shown, or may be conical. It is important, however, that the shield means 34 be provided with a relatively flat face or forward surface 3-5 spaced axially from the valve 23 and curved backstop 24 to divide the combustion chamber 11 into a forward entry compartment 36 and a downstream flame compartment 37. It is also essential that the baflle means have an outline when viewed in end at the fiat face 35 conforming essentially to the shape of the combustion chamber inner diameter to provide an annular gap 38 which is uniform in width entirely around the flat face 35 of the baflle means. By provision of a uniform annular gap 38 a ring of turbulence is created adjacent thereto which holds the residual flame for re-ignition, provides a restricted flow of hot, gases to the valve 23 to thereby reduce the operating temperature thereof, and restricts the combustion volume to accomplish greater compression and thereby promote more efficient combustion.

As was stated earlier, the baffle means 34 may comprise a relatively flat circular disc; however, a conical or hernispherical shape is preferred 'for the reason that a con,- yerging feed section is thereby provided which enhances restriction of flow of the hot gases to the valve means 23. Creation by the bafile means34 of an entry compartment 36 contributes importantly toward smoother eng'ne starting by providing a collection chamber for the starting mixture from the valve 23. In other words, the entry compartment 36 provides a reservoir supply which is in communication with the combustion chamber flame compartment only through the uniform annular gap 38, and

accordingly, a controlled flow of preheated starting mixture is directed to the flame compartment and a smoother ignition takes place. Further, and particularly with respect to the protection which the shield means 34 affords thevalve means 23, it may now be seen that the shield means increases the life of the petal valve by acting as a shock absorber and as a radiation barrier. Also, substantial experience has demonstrated that a marked reduction in the amount of carbon deposits on the petal valve 23 is accomplished, and thereby the frequency at which the jet unit 10 must be disassembled for cleaning is considerably reduced.

It hasbeen demonstrated that increased valve life and more eflicient engine operation result when a close relation is maintained between the respective volumes of the entry and flame compartments, and-the annular gap area carefully controlled with reference to the combustion.

chamber cross-sectional area. Specifically, it has been found that the volume of the entry compartment 36 should be not less than 10% of the volume of the flame compartment 37, nor be more than 25% of the volume of the compartment 37. It is to be understood in this con nection that the combustion chamber 11 comprises the two w p m s 36 an v 7 Th a o he a nu ar gap 38', on the other hand, should not'be more than onethe ,starting rnixturerpand -further improves starting, by

4 half of the combustion chamber cross-sectional area, nor less than one-fourth of said chamber cross-sectional area.

The bafile or shield means 34 may be supported in the combustion chamber 11 in various ways, and one manner of mounting is to'employ the bolt means 25 securing the curved backstop 24 to the base of the conical body member 26. For this purpose, the bolt means 25 has a portion 39 passing axially of the baffle means 34, the bolt portion 39 being threaded to receive nut means 40 and 41 bearing against the fiat face 35 and generally the center of dome portion 42 of the baffle means. It is to be noted that the bolt portion and nut means threaded thereon permit adjustment of the axial location of the shield means with respect to the valve 23 and backstop 24, to vary the respective volumes of the entry compartment 36 and flame compartment 37. The volume of the entry compartment with reference to the flame compartment may accordingly be varied or altered within the 10 to 25% range earlier noted.

A modified structural arrangement for mounting the baffle means within the combustion chamber is shown Figures 5 to 7 and reference is now made thereto. The bathe means and combustion chamber of the later figures are essentially identical to the corresponding parts of Figures 1 to 3, and the legends 34a and 11a have accordingly been appended to the bafiie and combustion chamber, respectively, of Figures 5 to 7.

The mounting means may comprise a plurality of circumferentially spaced rib members 43 located in the annular space 38a and receiving screws or the like 44 threaded through the combustion chamber wall and terminating in the baffle means 34a. The ribor supporting members 43 may be of teardrop shape in plan (Figure 6) to offer minimum resistance to fluid flow, and as appears in Fig. 7, may be contoured along the lower surface thereof to conform to the curvature of the bafl le means 34a. The advantage of the rib members 43, or means equivalent thereto, is that heat transfer to the: valve means 23 is minimized since there is no direct connection between the valve means or the baffle or shield means. Experience hasdemonstrated that the rib members provide no sub stantial interference to axial fluid flow in the combustion chamber 11a. Other means for supporting the bafile or shield in radially spaced relation to the combustion chamber and axially spaced from the valve means will be come apparent to those versed in the art.

It may now be seen that applicant has provided a novel jet engine of the resonating pulse type having improved starting and operating characteristics, and'wherein the valve means is effectively protected against over-heating or over-stressing. The shield or baflie means 34-protects the petal valve 23 by functioning as a radiation barrier, increases the life thereof by acting as a shock absorber, and restricts the flow of hot gases thereto and accordingly reduces the operating temperature of the valve means. Carbon deposition upon the petal valve is substantially reduced, and by effecting a temperature reduction .of the valve means the reliability of the entire jet unit 10 is markedly increased. The baflie means features adjustability and thereby it is now possible to controlthe location of the flame front and accomplish shield temperature reduction.

The shield or baffle is further effective to direct the fuel-air mixture against the combustion chamber walls to preheat the mixture, and when the baffle is constructed and arranged in the manner shown in the drawings, a restriction of the combustion volume is effected, and this in turn accomplishes greater compression and promotes more efficient combustion. Since the shield functions [as a constantly glowing ignition element, it is no longer necessary to place reliance upon residual flame in the combustion chamben The shield or baffie promotes starting by providing a collection or entry chamber for providinga ring of turbulence to hold the residual flame for re-ignition. And as a further advantage of smoother combustion, the engine noise level is reduced and irritating frequencies eliminated.

Various modifications may be effected in the structures herein disclosed without departing from the novel con cepts of the present invention.

I claim as my invention:

1. A pulse jet engine comprising, a combustion chamber and a valve assembly carried at one end defining a plurality of inlet ports, a valve member provided with a backstop and having portions overlying said ports, baffle means axially spaced from the valve member and backstop and spaced radially inwardly of the combustion chamber walls to prevent overheating of the valve member, and ignition means in said combustion chamber between said backstop and said baffie means for initially igniting an engine starting mixture, said baffle means promoting starting by providing a collection zone for said mixture.

2. A pulse jet engine comprising, a combustion chamber and a valve assembly carried at one end defining a plurality of inlet ports, a valve member having portions overlying said ports, bafi'le means in the combustion chamber downstream from the valve member and dividing the chamber into an entry compartment and flame compartment, and ignition means in said entry compartment between said valve member and said baffle means for initially igniting an engine starting mixture, the entry compartment providing a collection zone for the engine starting mixture and thereby promoting a smoother start of said engine.

3. A pulse jet engine comprising, a combustion chamber and a valve assembly carried at one end defining a plurality of inlet ports, a valve member having portions overlying said ports, and a dome-shaped shield member in the combustion chamber having a relatively flat surface dividing said chamber into entry and fiame compartments of relatively different volumes and a curved surface extending in an opposite axial direction from said valve chamber to provide a converging feed section enhancing restriction of flow of hot gases to said valve member, shid shield member having its flat surface axially spaced from the valve member and having an outer diameter of essentially the same outline as the inner diameter of the combustion chamber to define 4. A pulse jet engine comprising, a combustion chamher and a valve assembly carried-at one end defining a plurality of inlet ports, a valve member provided with a backstop and having portions overlying said supports, and a dome-shaped shield member in the combustion chamber having a relatively fiat surface dividing said chamber into entry and fiame compartments and a curved surface extending in an opposite axial direction from said valve member to provide a converging feed section enhancing restriction of flow of hot gases to said valve member, said shield member being axially spaced from the valve member and backstop and connected to the latter and having adjacent its relatively fiat surface an outer diameter of essentially the same outline as the inner diameter of the combustion chamber to define with said chamber a generally uniform annular gap restricting the flow of hot gases to the valve member to maintain the temperature thereof at proper operating levels, the annular gap area being not less than onefourth of the combustion chamber cross-sectional area and the entry compartment being of relatively lesser volume than the flame compartment.

5. In combination with a jet unit having a combustion chamber and an inlet'valve' in one end thereof provided I with a backstop, the improvement which comprises baffle means in the combustion chamber located downstream of the valve assembly and backstop in radially spaced relation to the combustion chamber walls and defining therewith an annular gap restricting the flow of hot gases to the valve assembly, the baffle means being of generally dome-shaped configuration having a relatively fiat surface axially spaced from the valve assembly and backstop and a curved surface extending downstream therefrom to provide a converging feed section enhancing restricting of fiow of hot gases to the valve assembly,

and means connecting with the valve assembly, backstop and baffle means for supporting said baffle means spaced from the valve assembly, backstop and combuswith said chamber a generally uniform annular gap reat proper operating tion chamber walls. 7

References Cited in the file of this patent UNITED STATES PATENTS 2,609,660 Tenney et al. Sept. 9, 1952 2,722,180 Mcllvaine Nov. 1, 1955 2,799,137 Tenney July 16, 1957 2,821,838 Zwicky Feb. 4, 1 958 

